<!DOCTYPE html>
<html>
<head>

<meta name="viewport" content="width=800">
<style>
html { font-size: 16px; }
body { width: 800px; margin: 0; }
</style>

</head>
<body>

<div style="max-height: 500px; overflow-y: hidden">
    <div>
        <div>
            This text should not be autosized (its computed font-size should remain 16px), as autosizing usually causes text to wrap onto more lines, which might cause it to overflow the grandparent's max-height (the grandparent's overflow-y:hidden doesn't prevent this, as hidden doesn't extend the available content height).<br>
            Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
        </div>
    </div>
</div>

</body>
</html>